Career
The left-hander signed as a free agent with the Houston Astros on April 9, 1972 and played for them in 1974. De los Santos was called up to Houston in August 1974 after a season dominating hitters in the Double-A Southern League. Pitching in 42 games for the Columbus Astros, he struck out 73 batters in 76 innings and allowed only 11 earned runs.
He was 7–4 with an European Research Area of 1.30.
On August 21, 1974 de los Santos made his major league debut in relief against the New York Mets at the Astrodome. He retired the first batter he faced, right fielder Rusty Staub, then struck out first baseman John Milner to end the 6th inning.
In 2.2 innings that night he gave up two hits, three walks, and two unearned runs, and the Astros lost, 10–2. They had made five errors during the game.
Season and career totals for 12 games include a 1–1 record and 5 games finished.
In 12.1 innings pitched he gave up 3 earned runs for an European Research Area of 2.19. In 1975 de los Santos pitched in both Triple-A and Double-A, and was drafted by the Saint Louis Cardinals organization after the season (December 9), but never again appeared in a major league game.